Stroke is a leading cause of disability, death and health care expenditure. Most strokes are ischemic (i.e. caused by a decrease in the blood supply to a portion of the brain due to a clot obstructing the flow of blood). A total or hemodynamically significant occlusion of a cerebral artery in an acute ischemic stroke is mostly due to thrombus formation, an embolus, and/or other unwanted matter.
When an artery is obstructed by thrombus, tissue ischemia (i.e. lack of oxygen and nutrients) quickly develops. One therapeutic goal of acute ischemic stroke treatment can be re-establishment of arterial patency, ideally prior to cell death caused by the ischemia. The sooner arterial patency is achieved the greater the clinical benefit, therefore, early restoration of blood flow in the affected territory of the brain may save brain tissue. Drug-based treatments can be used to dissolve the thrombus, but may take hours to take effect.
Fortunately, faster catheter-based thrombectomy treatments exist. Known thrombectomy treatments optionally make use of expandable stent-like devices to drag the occlusion along a blood vessel and into a catheter. One of the most popular devices currently used to perform a catheter based thrombectomy treatment is the Solitaire™ FR Revascularization Device, by ev3 Endovascular, Inc., which has a stent-like expandable cage. The Solitaire™ FR self-expands to a diameter of 4 mm or 6 mm when released, depending on the version selected for use. These self-expanding structures seek to capture the thrombus and may pull at least a portion of the thrombus into a retrieval catheter for removal from the vessel.
While often effective, known thrombus-removal devices, systems, and methods suffer from significant limitations. In particular, expansion forces between self-expanding structures and the vessel wall may vary primarily with the size of the device and the size of the area in which the device is constrained, with the devices often applying forces that increase when the size of the vessel or opening is smaller. Even when the correct size device is initially selected to initially secure the thrombus, the device may not be ideal for moving the thrombus into the retrieval catheter, particularly if the retrieval catheter is positioned at a significant distance from a difficult-to-remove thrombus mass, when the vessel varies in size, has one or more bends, and/or has one or more branches between the thrombus and the retrieval catheter.